Caused by sparking at the brushes, commutator machines are known to disseminate strong radio noise fields. As nowadays cars are equipped with sensitive electronic sensors and microprocessors, which are sensitive to noise signals on supply voltages and radio fields the suppression of such noise signals have become more and more important. When an electric current that drives a motor flows through an electrode, electromagnetic noise is generated. The electromagnetic noise is electromagnetic interference (EMI) and interferes with other electronic equipment, thereby causing malfunction. In recent car models, a lot of electronic equipments are used and in order to prevent malfunction due to electromagnetic interference, improvement in characteristic for the electromagnetic interference prevention in a motor is required. In order to cope with this problem it is known to use EMI suppression elements at appropriate locations. As voltage supply wires and signal wires have to enter or leave the motor the shield of a completely shielded electric motor is vulnerable by little openings.
In order to keep the openings as small as possible it is known to guide wires into the electric motor by feed through capacitors.
The use of feed through capacitors however is a relative costly solution.
Additionally, a sensor magnet is directly or indirectly fixed to a shaft. Since the shaft slightly moves in an axial direction, the sensor magnet also moves in the axial direction. In a case where a sheet of circuit board is used, a distance as far as a magnetic pole sensor increases. For this reason, a detection error width increases.
The detection error width can be reduced by aligning the axial heights of the sensor magnet and the magnetic pole sensor. However, in this case, the magnetic pole sensor is disposed at the center of the circuit board, and thus it is not possible to dispose electronic components for EMC measures together. Therefore, in a case where it is not possible to dispose the electronic components for EMC measures together, since a wiring in the circuit board becomes longer, electromagnetic noise is easily generated, and thus it is not preferable.